| 摘要 |
PURPOSE:To simplify a constitution, by performing the conversion of a sampling frequency by the combination of a digital circuit and an analog circuit. CONSTITUTION:An analog waveform (a) in the fig. A is obtained by passing a PCM signal at an input terminal 1 through a D/A converter 6 and an LPF7, a signal waveform (b) after delay is obtained at delay lines D.L. from an analog output signal of the converter 6. Thus, a waveform (c) in the fig. B is outputted from a difference signal arithmetic circuit 9. The waveform (c) is sampled with a sampling clock signal of a receiving side PCM device at an A/D converter 10, where the A/D conversion is attained. A PCM signal outputted from the converter 10 and a PCM signal delayed at a digital delay circuit D at the input terminal 1 are fully added digitally at an adder 11 and reduced to an output PCM signal to be fed to the receiving PCM device. Since the difference signal of adjacent sampling levels is A/D-converted, the required bit number of the converter 10 is less than that of the PCM signal, the accuracy required for the A/D converter is mitigated, and an inexpensive A/D converter is usable. |
